The proposal is to depict two sea waves "waving" in opposite directions

One across the left border of the tile, the other across the left right border of the tile

The first file has taller waves, the second smalls waves

Thanks. The problem is that moving the waves every frame is way too fast for a pleasant result. This is what I have come up with in the meantime after several attempts. It is moving two lines at a time every 4 frames, only one pixel back and forth .

I have been agonizing over execution speed: Should the game scroll faster (30 or 20 frames per second (FPS)) when the graphics are simple, or scroll at a constant speed of 15 FPS and perhaps waste a lot of clock cycles? This decision has to be taken early because even though I have fixed the game loop at 30 FPS there's still the coordination with the background to consider. I ended up deciding in favor of the fixed frame rate with the hope that some of the clock cycles may be spent on sprite handling rather than busy waiting.

Anyway, a few more features and a few more enemies now. You can be hit but you respawn right after. Edit: and you get points for the few enemies there are.

I found the cure for the slow-down in the music although I don't fully understand the reason. I just had to call the sound player before my main wait for vsync if and only if an interrupt has already occurred. Apart from that this version only includes a few new sound FXs.

It's better and better! Thanks! :-D
Alas, I have no time to build a 512Kb pcb cartridge and I would like so much to use a real hardware for the demo. So, Ramus could you propose a floppy disk version? Thank you by advance !

It's better and better! Thanks!
Alas, I have no time to build a 512Kb pcb cartridge and I would like so much to use a real hardware for the demo. So, Ramus could you propose a floppy disk version? Thank you by advance !

A floppy disk version would require SAMS, and I'm not planning to go down that route. But when the game is finished it will be available on cartridge.

I also watched some comparing videos and i must say that this version has lot of power compared at some other conversions.

The best one of the exist conversion of this game i think is the C64's one, i like the music and sound effects really near to the original arcade version.

about sound effects on the TI99 i think that the airplane gun's sound could be changed in something similar to a gun for an old airplane, the current FX remember me a laser, but it is not important anyway just my impression